According to reports, her doctors ordered her to get some rest due to dehydration and exhaustion. And although Bey herself has never canceled a show, this was a tough decision for her to make. However, she did follow doctor's orders.

"I've never postponed a show in my life. It was very hard for me. I promise I will make it up very soon. I'm sorry if I disappointed you," she wrote in the letter (seen below) posted on her website.

iam.beyonce.com

She informed fans that she's feeling much better and will make up for the postponed concert during tonight's (May 15) second scheduled show in Antwerp.